Expect I will use some Adobe stock soon and therefore the monthly 10 photo plan seems promising. I will be using the resources to illustrate explainer documents (pdfs) that will go up on a website and can be downloaded by users. The website is not built yet so current users stand at 0.
However, what happens if users exceed 500,000 at some point in the future? Would i need to upgrade my licenses then? Seems a bit flippant to do that now (v expensive) when it may never happen). Does Adobe send the lawyers in as soon as site visitors reach 500,000 (!!)
You didn't mention if you were selling the PDFs or not. How are the images being used exactly? Meaning are they the main value of the document?
You can upgrade to an Extended License if the need arises. You can start with a Standard license providing it meets the terms.
Not selling the pdf's - they'd just be additional explainers to illustrate the various features of the website / business concept. Far removed from commercial purpose, purely educational.
You should be fine starting out with the Standard license. Always a good idea to include small photo credits somewhere in the document though if using Standard license.